code: def sigma_sq(self, sample, funcs, func_params):
      ret = 0
      for i in range(1, self.step + 1):
          temp = self.interm_res[i - 1] - self.f_comb(
              i, sample, funcs, func_params
          )
          ret += temp * temp
      return 1.0 * ret / self.step
  
imports: import scipy
  import logging
  import numpy
  import time
  from scipy import optimize
label_desc: Use image node_id 6 for calling the CurveModel obj's underlying member method code with example usage: obj.sigma_sq(sample, funcs, func_params) and returns: unknown